Screening effect of plasma flow on the resonant magnetic perturbation penetration in tokamak based on two-fluid model

TL;DR

This study uses a two-fluid model to simulate magnetic perturbation penetration in tokamaks, revealing the stabilizing role of diamagnetic drift flow and a novel oscillation phenomenon of magnetic islands.

Contribution

It introduces a new simulation approach incorporating bootstrap current and drift flows, providing insights into mode penetration and stabilization mechanisms in tokamaks.

Findings

Diamagnetic drift flow can strongly stabilize neoclassical tearing modes.

A mode penetration phenomenon different from classical models is observed.

An oscillation of magnetic island width due to pressure feedback is identified.

Abstract

Numerical simulation on the resonant magnetic perturbation penetration is carried out by the newly-updated initial value code MDC (MHD@Dalian Code). Based on a set of two-fluid four-field equations, the bootstrap current, parallel and perpendicular transport effects are included appropriately. Taking into account the bootstrap current, a mode penetration like phenomenon is found, which is essentially different from the classical tearing mode model. It may provide a possible explanation for the finite mode penetration threshold at zero rotation detected in experiments. To reveal the influence of diamagnetic drift flow on the mode penetration process, $\bf E\times B$ drift flow and diamagnetic drift flow are separately applied to compare their effects. Numerical results show that, a sufficiently large diamagnetic drift flow can drive a strong stabilizing effect on the neoclassical tearing mode. Furthermore, an oscillation phenomenon of island width is discovered. By analyzing in depth, it is found that, this oscillation phenomenon is due to the negative feedback regulation of pressure on the magnetic island. This physical mechanism is verified again by key parameter scanning.